# log1p
> Evaluate the [natural logarithm][@stdlib/math/base/special/ln] of `1+x`.
## Usage
```javascript
var log1p = require( '@stdlib/math/base/special/log1p' );
```
#### log1p( x )
Evaluates the [natural logarithm][@stdlib/math/base/special/ln] of `1+x`.
```javascript
var v = log1p( 4.0 );
// returns ~1.609
v = log1p( -1.0 );
// returns -Infinity
v = log1p( Infinity );
// returns Infinity
v = log1p( 0.0 );
// returns 0.0
v = log1p( -0.0 );
// returns -0.0
v = log1p( NaN );
// returns NaN
```
For `x < -1`, the function returns `NaN`, as the [natural logarithm][@stdlib/math/base/special/ln] is **not** defined for negative numbers.
```javascript
var v = log1p( -2.0 );
// returns NaN
```
## Examples
```javascript
var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var log1p = require( '@stdlib/math/base/special/log1p' );
var x;
var i;
for ( i = 0; i < 100; i++ ) {
x = round( randu() * 100.0 );
console.log( log1p( x ) );
}
```
[@stdlib/math/base/special/ln]: https://www.npmjs.com/package/@stdlib/math/tree/main/base/special/ln